1,915 research outputs found
Cognitive Radio with Partial Channel State Information at the Transmitter
In this paper, we present the cognitive radio system design with partial
channel state information known at the transmitter (CSIT).We replace the dirty
paper coding (DPC) used in the cognitive radio with full CSIT by the linear
assignment Gel'fand-Pinsker coding (LA-GPC), which can utilize the limited
knowledge of the channel more efficiently. Based on the achievable rate derived
from the LA-GPC, two optimization problems under the fast and slow fading
channels are formulated. We derive semianalytical solutions to find the
relaying ratios and precoding coefficients. The critical observation is that
the complex rate functions in these problems are closely related to ratios of
quadratic form. Simulation results show that the proposed semi-analytical
solutions perform close to the optimal solutions found by brute-force search,
and outperform the systems based on naive DPC. Asymptotic analysis also shows
that these solutions converge to the optimal ones solved with full CSIT when
the K-factor of Rician channel approaches infinity. Moreover, a new coding
scheme is proposed to implement the LA-GPC in practice. Simulation results show
that the proposed practical coding scheme can efficiently reach the theoretical
rate performance.Comment: resubmitted to IEEE Transaction on Wireless Communications, May 200
Stochastic Differential Games and Energy-Efficient Power Control
One of the contributions of this work is to formulate the problem of
energy-efficient power control in multiple access channels (namely, channels
which comprise several transmitters and one receiver) as a stochastic
differential game. The players are the transmitters who adapt their power level
to the quality of their time-varying link with the receiver, their battery
level, and the strategy updates of the others. The proposed model not only
allows one to take into account long-term strategic interactions but also
long-term energy constraints. A simple sufficient condition for the existence
of a Nash equilibrium in this game is provided and shown to be verified in a
typical scenario. As the uniqueness and determination of equilibria are
difficult issues in general, especially when the number of players goes large,
we move to two special cases: the single player case which gives us some useful
insights of practical interest and allows one to make connections with the case
of large number of players. The latter case is treated with a mean-field game
approach for which reasonable sufficient conditions for convergence and
uniqueness are provided. Remarkably, this recent approach for large system
analysis shows how scalability can be dealt with in large games and only relies
on the individual state information assumption.Comment: The final publication is available at
http://www.springerlink.com/openurl.asp?genre=article\&id=doi:10.1007/s13235-012-0068-
Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey
This paper provides a comprehensive review of the domain of physical layer
security in multiuser wireless networks. The essential premise of
physical-layer security is to enable the exchange of confidential messages over
a wireless medium in the presence of unauthorized eavesdroppers without relying
on higher-layer encryption. This can be achieved primarily in two ways: without
the need for a secret key by intelligently designing transmit coding
strategies, or by exploiting the wireless communication medium to develop
secret keys over public channels. The survey begins with an overview of the
foundations dating back to the pioneering work of Shannon and Wyner on
information-theoretic security. We then describe the evolution of secure
transmission strategies from point-to-point channels to multiple-antenna
systems, followed by generalizations to multiuser broadcast, multiple-access,
interference, and relay networks. Secret-key generation and establishment
protocols based on physical layer mechanisms are subsequently covered.
Approaches for secrecy based on channel coding design are then examined, along
with a description of inter-disciplinary approaches based on game theory and
stochastic geometry. The associated problem of physical-layer message
authentication is also introduced briefly. The survey concludes with
observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with
arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials,
201
Throughput of a Cognitive Radio Network under Congestion Constraints: A Network-Level Study
In this paper we analyze a cognitive radio network with one primary and one
secondary transmitter, in which the primary transmitter has bursty arrivals
while the secondary node is assumed to be saturated (i.e. always has a packet
waiting to be transmitted). The secondary node transmits in a cognitive way
such that it does not impede the performance of the primary node. We assume
that the receivers have multipacket reception (MPR) capabilities and that the
secondary node can take advantage of the MPR capability by transmitting
simultaneously with the primary under certain conditions. We obtain analytical
expressions for the stationary distribution of the primary node queue and we
also provide conditions for its stability. Finally, we provide expressions for
the aggregate throughput of the network as well as for the throughput at the
secondary node.Comment: Presented at CROWNCOM 201
Mean Field Energy Games in Wireless Networks
This work tackles the problem of energy-efficient distributed power control
in wireless networks with a large number of transmitters. The problem is
modeled by a dynamic game. Each transmitter-receiver communication is
characterized by a state given by the available energy and/or the individual
channel state and whose evolution is governed by certain dynamics. Since
equilibrium analysis in such a (stochastic) game is generally difficult and
even impossible, the problem is approximated by exploiting the large system
assumption. Under an appropriate exchangeability assumption, the corresponding
mean field game is well defined and studied in detail for special cases. The
main contribution of this work is to show how mean field games can be applied
to the problem under investigation and provide illustrative numerical results.
Our results indicate that this approach can lead to significant gains in terms
of energy-efficiency at the resulting equilibrium.Comment: IEEE Proc. of Asilomar Conf. on Signals, Systems, and Computers, Nov.
2012, Pacific Grove, CA, US
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